Protocol for Macroscopic and Microscopic Urinalysis and Investigation of Urinary Tract Infections

Transcription

1 Protocol for Macroscopic and Microscopic Urinalysis and Investigation of Urinary Tract Infections Reprinted 2004 Scope The purpose of this protocol is to avoid unnecessary testing in routine cases while allowing physicians to order tests justified by the patient s clinical condition in special cases. This protocol applies to: samples analysed in a physician s office or referred to a laboratory for routine analysis of urine; and, midstream samples referred for urine culture or conditional requests for culture in patients with suspected urinary tract infections. It does not apply to individuals under 19 years of age, catheter or bagged specimens, or suprapubic aspirations. Laboratories may now perform a microscopic urinalysis without a preceding macroscopic urinalysis (dipstick) when: positive macroscopic result was obtained in the physician s office; or, the physician has requested an order for a urine culture, conditional on the results of the microscopic. RECOMMENDATION 1 Urinalysis When UTI Not Suspected Negative macroscopic-screened urines do not routinely require microscopic examination of urine sediment. Microscopic examination of urine sediment will be when requested only under the following conditions: a) positive macroscopic result: macroscopic examination positive for any of the following: blood (Hb), protein (greater than trace), nitrite, leukocyte esterase, turbidity, or glucose concentration greater than 55 mmol/l; or, b) special case: patients presenting with a condition where the clinical record justifies further investigation such as: spinal cord injury or disease (including paraplegia or quadriplegia) neurogenic bladder recent urological surgery/cystoscopy established kidney disease BRITISH COLUMBIA MEDICAL ASSOCIATION

2 kidney transplant genitourinary problems (nephrolithiasis, bladder calculi, congenital or developmental anatomic abnormalities) pregnancy diabetes recurrent urinary tract infections requests by consultant physicians for the investigation of urinary tract problems. Note: Other choices for urinalysis on the requisition include: Macroscopic (dipstick) Microscopic If one of these is checked, the test will be as requested. If both are checked, the request will be treated as Macroscopic microscopic if dipstick positive. Macroscopic microscopic if dipstick positive Macroscopic and microscopic, provide indication above Macroscopic Macroscopic and microscopic Positive Negative Microscopic Microscopic NOT RECOMMENDATION 2 UTI Suspected If an uncomplicated UTI is suspected in a patient with classic symptoms and treatment is not conditional on culture or sensitivity results (i.e. if antibiotics have been prescribed), then no further testing is necessary. If an uncomplicated UTI is suspected in a patient with classic symptoms and treatment is conditional on culture or sensitivity, then urine culture alone should be requested. If urine culture and any combination of macroscopic and/or microscopic urinalysis are ordered, urinalysis will be according to the rules outlined in Recommendation 1, and urine culture will be regardless of the results of macroscopic and/or microscopic urinalysis. If urine culture is requested without an accompanying request for urinalysis, a urine culture will be. RECOMMENDATION 3 UTI Suspected - Conditional Request for Culture When a urinalysis - urine culture if pyuria or nitrite present is requested, either a macroscopic or a microscopic urinalysis,* but not both, will be. A urine culture will then be only if: a macroscopic urinalysis is positive for leukocyte esterase and/or nitrite; or, a microscopic urinalysis is positive for white blood cells.** 2 2

3 * The choice of macroscopic or microscopic urinalysis will be made by the laboratory unless the referring physician requests microscopic. ** Positive for white blood cells must be defined by the local laboratory physician. Urinalysis urine culture if pyuria or nitrite present Macroscopic or microscopic Positive Negative Culture Culture NOT Rationale The purpose of this protocol is to avoid unnecessary testing in routine cases while allowing physicians to order tests justified by the patient s clinical condition in special cases. Routine Urinalysis Various studies have examined whether macroscopic screening urinalysis can predict the need for further microscopic assessment of urinary sediment While some studies have supported microscopic assessment of all urines, regardless of macroscopic results, 1-3 others support microscopic analysis only in certain patient populations. 4 The majority, however, have concluded that microscopic examination of urine sediment is not necessary if initial macroscopic screening is negative. 12 Notable exceptions are urinalysis for patients with spinal cord injury, quadriplegic or paraplegic patients with no voluntary urine control, and patients with genitourinary problems (e.g. nephrolithiasis, bladder calculi, congenital or developmental anatomic abnormalities). 4 The latter two patient categories account for about half of the false negative macroscopic screening results. 4 Macroscopic test results positive for certain components are rarely correlated with positive microscopic examination of urine sediment. A study of 1385 specimens, positive for ph, SG, urobilinogen, bilirubin, ketone, or glucose, found that less than 0.5% were associated with positive microscopic examinations of urine sediment. Macroscopic tests positive for blood (Hb), protein and turbidity, however, are more likely to be associated with positive microscopic examination or urine sediment. 4 Macroscopic tests positive for leukocyte esterase and nitrite are highly correlated with positive microscopic examinations of urine sediment. 4,13-16 Since high glucose concentration interferes with leukocyte esterase, a glucose concentration greater than 55 mmol/l may be considered an appropriate justification for proceeding to microscopic urinalysis. 3

4 Investigation of Urinary Tract Infection The costs associated with the investigation of urinary tract infection (UTI) are substantial. However, up to 60-80% of all urine samples sent to the lab for culture are reported negative for bacteria. 17 To reduce the costs of unnecessary testing in the investigation of UTI, the ordering physician should consider whether the test(s) ordered will modify the patient s management. The likelihood of a significant urine culture in the absence of pyuria or nitrite in a midstream specimen is low When a urine culture or conditional request for culture is submitted, a midstream sample must be collected. It is important to follow proper technique to prevent contamination (consult your laboratory for details). If urinalysis is required before urine culture, microscopic urinalysis is preferable to macroscopic because of its higher sensitivity and specificity Macroscopic (dipstick) urinalysis may, however, provide a useful aid for the rapid diagnosis of urinary tract infections for physicians who do not have access to a microscope. If pyuria is found on the dipstick in the physician s office, further microscopic urinalysis may not be necessary. It is rarely necessary to order both a macroscopic and a microscopic urinalysis with a urine culture except for special cases (see Recommendation 1). Some laboratories may prefer to perform macroscopic urinalysis to facilitate processing since the difference in sensitivity between macroscopic and microscopic is considered to be relatively small. Physicians concerned about the difference in sensitivity may wish to request microscopic urinalysis on the requisition. In uncomplicated community-acquired cystitis, culture is rarely required when antibiotics are being prescribed. Furthermore, follow-up cultures are not routinely indicated in asymptomatic patients with uncomplicated urinary tract infections. References 1. Szwed JJ, Schaust C. The importance of microscopic examination of the urinary sediment. Am J Med Tech 1982;48(2): Nanji AA, Adam W, Campbell DJ. Routine microscopic examination of the urine sediment. Should we continue? Arch Pathol Lab Med 1984;108(5): Resnick M. Simplifying urinalysis. Clin Chem 1985;31(3): Morrison MC, Lum G. Dipstick testing of urine - can it replace urine microscopy? Am J Clin Pathol 1986;85(5): Schumann GB, Greenberg, NF. Usefulness of macroscopic urinalysis as a screening procedure - a preliminary report. Am J Clin Pathol 1979;71(4): Smalley DL, Bryan JA. Comparative evaluation of biochemical and microscopic urinalysis. Am J Med Tech 1983;49(4): Bartlett RC, Kaczmarczyk LA. Usefulness of microscopic examination in urinalysis. Am J Clin Pathol 1984;82(6): Valenstein PN, Koepke JA. Unnecessary microscopy in routine urinalysis. Am J Clin Pathol 1984;82(4): Valenstein PN, Koepke JA. Routine microscopic examination of the urine sediment revisited. Arch Pathol Lab Med 1984;108(11): Freedman SI. Routine microscopic examination of the urine sediment revisited. Arch Pathol Lab Med 1984;108(11): Shaw ST, Poon SY, Wong ET. Routine urinalysis - is the dipstick enough? JAMA 1985;253(11): Cramer AD, Chogyoje M, Saxena S, Appleman MD, Wong ET. Macroscopic screening urinalysis. Lab Med 1989;20(9): Bartlett RC, ONeil D, Mclaughlin JC. Detection of bacteriuria by leukocyte esterase, nitrite, and the automicrobic system. Am J Clin Pathol 1984;82(6): Wenk RE, Dutta D, Rudert J, Kim Y, Steinhagen C. Sediment microscopy for pyuria vs. nitrite esterase reactions as detectors of significant bacteriuria. Am J Clin Pathol 1982;78(2):

5 15. Borland PC, Stoker M. Dipstick analysis for screening of pediatric urine. J Clin Pathol 1986;39(12): Marsik FJ, Owens D, Lewandowski J. Use of the leukocyte esterase and nitrite tests to determine the need for culturing urine specimens from a pediatric and adolescent population. Diagn Microbiol Infect Dis 1986;4(2): Onderkonk AB, Winkelman JW, Orni-Wasserlauf R. Eliminating unnecessary urine cultures to reduce costs. Lab Med 1996; 27(12): Ditchburn RK, Ditchburn JS. A study of microscopical and chemical tests for the rapid diagnosis of urinary tract infections in general practice. Br J Gen Pract 1990; 40: Papas PG. Laboratory in the diagnosisand management of urinary tract infections. Med Clin North Am 1991; 75(2): Bailey BL. Urinalysis predictive of urine culture results. J Fam Pract 1995; 40(6): Blum RN, Wright RA. Detection of pyuria and bacteriuria in symptomatic ambulatory women. J Gen Intern Med 1992; 7(2): Mandell GL, Douglas RG, Bennett JE, Dolin R. Principles and practice of infectious diseases. 4th ed. New York: Churchill Livingstone, pg 669. Administration and Audit Implications Sponsors This guideline was developed by the Guidelines and Protocols Advisory Committee, approved by the British Columbia Medical Association and adopted by the Medical Services Commission. Partial funding for this guideline was provided by the Health Canada Primary Health Care Transition Fund Effective Date: May 1, 2005 This guideline is based on scientific evidence current as of the effective date. Guidelines and Protocols Advisory Committee Blanshard Street Victoria BC V8W 3C8 Phone: Fax: hlth.guidelines@gems6.gov.bc.ca Web site: The principles of the Guidelines and Protocols Advisory Committee are: to encourage appropriate responses to common medical situations to recommend actions that are sufficient and efficient, neither excessive nor deficient to permit exceptions when justified by clinical circumstances. 5 G&P